DIFFERENTIAL-EFFECTS OF LEARNING AND RECALL OF A SPATIAL TASK ON PHOSPHOINOSITIDE HYDROLYSIS INDUCED BY THE METABOTROPIC GLUTAMATE-RECEPTORAGONIST 1(S),3(R)-ACPD (1(S),3(R)-1-AMINO-CYCLOPENTANE-1,3-DICARBOXYLIC ACID) IN THE HIPPOCAMPUS AND THE PREFRONTAL CORTEX OF RATS

Phosphoinositide (PI) hydrolysis, stimulated by 1(S),3(R)-1-amino-cycl opentane-1,3-dicarboxylic acid (1(S),3(R)-ACPD), an agonist of metabot ropic glutamate receptors (mGluRs), was measured in hippocampal and pr efrontal cortical slices obtained from rats which had been trained for 8 days in a Morris water maze and had learned an allocentric spatial task. Brain slices were pre-labeled with myo[H-3]inositol and 1(S)3(R) -ACPD (100 mu M) stimulation was assessed by measuring the accumulatio n of [H-3]inositol phosphates ([H-3]IPs) in the presence of Li+. Measu rements conducted 24 h following the last training session revealed no differences in 1(S)3(R)-ACPD-stimulated formation of [H-3]IPs, either in the hippocampus or in the prefrontal cortex. However, a diminished response to mGluRs stimulation was detected in the hippocampus of ani mals re-trained after an 11-day interval. The decrease was not evident in the prefrontal cortex. These data indicate a differential involvem ent of the hippocampus and the prefrontal cortex in the processing of spatial information and correspond to the functional differences attri buted to these areas.